The presently disclosed subject matter relates to a strain relief for reducing burden on a connection part between two members, and a catheter provided with the strain relief.
In general, a catheter for use in the medical field has a long flexible (bendable) shaft section (tubular body), and a rigid hub connected (joined) to a proximal portion of the shaft section. When used (operated), the catheter is liable to stress concentration at the connection part between the shaft section and the hub, possibly resulting in damage due to bending of the shaft section (this phenomenon is sometimes called kinking). To cope with this problem, a strain relief for enhancing the strength of the connection part between the shaft section and the hub is often provided at the connection part.
For example, U.S. Pat. No. 6,068,622 (hereinafter referred to as Patent Document 1) discloses a strain relief provided with a strain relief coil which, during use, encloses a proximal-side circumferential surface of a catheter body. The strain relief coil is a continuous coil of constant or variable pitch having coil turns that decrease in diameter from the proximal strain relief coil end to the distal strain relief coil end. The turns of the strain relief coil are preferably molded over a distal portion of exterior surface of the catheter body in the catheter hub/body junction and adhered in a spiral pattern to the exterior surface of the catheter body. In this strain relief, each turn of the coil comes closer to and further away from an adjacent turn in the coil through elastic deformation. The axial distance between coil turns (i.e., pitch) can vary along the axial length, and the strain relief as a whole is curved.
Another strain relief disclosed in U.S. Published Patent Application No. 2001/0049519 (hereinafter referred to as Patent Document 2) includes a plurality of grooves which enclose a shaft section (tube). In the strain relief disclosed in Patent Document 2, the width and spacing of the grooves may be varied to effect the flexibility of strain relief. Each groove extends through the strain relief leaving a thin portion of strain relief disposed between oppositely disposed grooves. This strain relief is more flexible at a distal end than at its proximal end. The thin portion provides a point of flexibility or transverse hinge in the strain relief. When a generally transverse bending force is applied to the strain relief, grooves on the opposite side of strain relief from the bending force will tend to close as grooves on the same side of the strain relief as the force tend to open. In short, the strain reliefs disclosed in Patent Documents 1 and 2 are so configured as to elastically support the shaft section and to disperse the load exerted on the connection part between the shaft section and the hub, thereby restraining the kinking phenomenon.